The present disclosure relates generally to flexible light emitting diode (LED) assemblies and their applications, more specifically to the LED assemblies suitable for omnidirectional light appliances.
LED has been used in different kinds of appliances in our life, such as traffic lights, car headlights, street lamps, computer indicators, flashlights, LCD backlight modules, and so on. LED chips as light sources for appliances are produced by wafer manufacturing process in the front end, and then undergo LED packaging in the back end to result in LED assemblies or apparatuses.
LED packaging mainly provides mechanical, electrical, thermal, and optical supports to LED chips. LED chips, which are kind of semiconductor products, are prone to performance degradation, or aging, if exposed for a long time in an atmosphere of humidity or chemical. To isolate the LED chips from the unfriendly atmosphere, epoxy resins are commonly used to cover and seal them. Heat dissipation and light extraction should be also considered for LED packaging, such that LED products could have long lifespan, high brightness and power conservation. For example, the heat generated by an LED chip, if not well dissipated, could deteriorate the LED chip, shorten its lifespan, and downgrade its reliability. Optical design, such as the way to extract and direct the light into a preferable angle or distribution, also plays an important role for LED packaging.
Design for packaged white LEDs is more complicated and needs further consideration of color temperature, color rendering index, phosphor, etc. A white LED could be provided by using phosphor to convert a portion of the blue light from a blue LED chip into green/yellow light, such that the mixture of the lights is perceived as white light by human eyes. Because human eyes are vulnerable to high-intensity blue light, the blue light from a blue LED chip in a white LED package should not emit outward directly without its intensity being attenuated by phosphor. In other words, the blue light should be kind of “sealed” or “capsulated” by phosphor inside a white LED package so as to prevent blue light from leakage to human eyes.